Introduction
Subacromial impingement syndrome (SIS) is the most commonly reported shoulder pathology that affects various aspects of patients' daily activities. It implies the mechanical compression of rotator cuff tendons, long head of biceps and subacromial/subdeltoid bursae under the coracoacromial arch. Treatment remains controversial as implicated by its multifactorial nature and its disparate theories of pathogenesis. Recently, L-GF has proved to be an effective novel injection material. It is thus interesting to study its effect on SIS.

Methods
Sixty patients with SIS were included in the study. Patients were identified as having SIS when clinically they had anterolateral shoulder pain, a painful arc of motion and positive impingement signs. The study was double blind. Patients were randomly divided to receive either saline or L-GF injection, under ultrasonographic guidance.

Results
There was no statistically significant difference between the two groups as regards age, disease duration and gender.
The L-GF group has shown greater reduction in VAS score at follow up. There was statistically significant improvement in both active and passive internal rotation ROM in the L-GF group at follow up. Only the L-GF group has shown statistically significant improvement regarding SPADI-Disability scale as well as significant improvement in the longitudinal thickness of the supraspinatus tendon at follow up.

Conclusion
From this study it can be concluded that L-GF injection in patients with SIS has resulted in significant improvement as regards pain and disability as well as significant reduction in supraspinatus tendon thickness as measured by ultrasound compared to the saline group.